Sheet metal articles are conventionally produced by forming low carbon steel or aluminum-alloy sheet stock into desired panel shapes, often by conventional room temperature processes such as stamping. Such articles, however, can also be produced by hot blow-forming processes that use complementary forming tools in a press under the pressure of a working gas to stretch-form a preheated sheet metal blank against forming surfaces on the forming tools. Such processes are typically known as super-plastic-forming (SPF) and quick-plastic-forming (QPF), and are particularly applicable to forming blank sheet metal into products of complex three-dimensional curvature, such as automotive body panels.
In particular, QPF tooling is integrally heated to provide more localized heating closer to the workpiece at the forming surface of the tooling. Accordingly, QPF tooling includes internal heating elements embedded therein to provide the heat necessary to carry out the hot blow-forming process. Much of the heat generated by the internal heating elements is efficiently directed toward the forming surface as intended. Some heat, however, is lost via thermal conduction through the tooling and into the press to which the tooling is attached. Also, some heat is lost via thermal radiation from the tooling and into the surrounding ambient shop environment. Thus, it is an object of this invention to provide tooling for a hot blow-forming process that is structured to minimize thermal losses of the tooling and thereby increase the thermal efficiency of the process.